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Evidence of

Evidence of. Evolution. FOR EVOLUTION. Evidence of Evolution. 1. Fossils 2. Geographic Distribution 3. Homologies. Fossil Record. What is a fossil ? - T he preserved remains of a once-living organism. How do fossils help scientists ? 1. Tells us what organisms lived long ago

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Evidence of

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  1. Evidence of Evolution FOR EVOLUTION

  2. Evidence of Evolution 1. Fossils 2. Geographic Distribution 3. Homologies

  3. Fossil Record What is a fossil? -The preserved remains of a once-living organism. How do fossilshelp scientists? 1. Tells us what organisms lived long ago 2. Shows how the Earth’s surface has changed. 3. Help us understand what past environments may have been like.

  4. How do we get fossils? Fossils are formed in SEDIMENTARY ROCK. If an organism dies and is buried by sediment rock, it’s bones are protected from rotting. Over time, more sediment layers build on top of the remains. Minerals replace all or part of the organism’s body. The preserved remains may later become exposed by erosion or the Earth’s movement.

  5. How do we know the age of fossils? You have to DATE them!

  6. Which fossil came first? • Relative Dating Age of fossils RELATIVE to other rocks or fossils. 2. Radioactive dating ACTUALage of fossils using the half life of radioactive isotopes

  7. How does Relative Dating work? Rock layers form in order of age – the oldest layers on the bottom and the youngest on the top. Scientists use index fossils to compare the ages of fossils. Index fossil: a species easily recognizable, existed for a short period of time, and wide geographic range. *** Does NOT give age in years*** A B C D E

  8. How does Relative Dating work? A Looking at this mountain, where would you expect to find the oldest fossils? B C D E

  9. Which is older D or F? Index Fossils Found Fossils

  10. How Does Radioactive Dating Work? Throughout an organism’s life, it takes in Carbon-14. Once the organism dies it no longer takes in Carbon-14. The C-14 present in the plant or animal begins to decay at a certain rate called half-life. Half-life: the length of time required for half the radioactive atoms in an organism to decay. Carbon-14 half life: 5,730 years

  11. How does Radioactive Dating work? Carbon-14 is one example of radioactive dating. It is useful for dating fossils younger than 60,000 years. To date older rocks, researchers use elements with longer half-lives. Potassium-40 half-life: 1.26 billion years

  12. Let’s Practice! How much of a 100g amount of carbon-14 would be left after 17,340 years? Carbon-14 half life: 5,730 Answer: 12.5g

  13. Decay of Carbon-14 What do you notice about the percent of original C-14 remaining?

  14. Geographical Distribution Similar animals in living different locations are the product of different lines of evolutionary descent.

  15. Homologous Structures Homologous Structure: structures that have different mature forms but develop from the same embryonic tissues. Homologous structures provide strong evidence that all four-limbed vertebrates have descended, with modifications, from common ancestors.

  16. Homologous Structures Not all homologous structures serve important functions. Vestigial organs: Organs in animals that are reduced in size to where they are just traces of homologous organs in other species.

  17. Analogous Structures Analogous Structure: the similarity of structure between two species that are not closely related. • Which structures are analogous? Homologous? Answer: Analogous- Bird to Insect, Bat to Insect Homologous- bird and bat wings

  18. How do Analogous Structures Occur? Convergent Evolution: Species from different evolutionary branches may come to resemble one another if they live in very similar environments. Natural Selection may result in body structures and even whole organisms that look very similar without having the same common ancestor.

  19. Embryology Pig Human Rabbit Cow Comparative Embryology: the comparison of early stages of development Pharyngeal (throat) pouches in embryotic stages shows one sign that vertebrates evolved from a common ancestor.

  20. Molecular Biology Molecular Biology studies amino acid sequences of similar proteins in different species to discover the molecular history of evolution and common ancestor.

  21. Molecular Biology Molecular Biology is the BEST WAYto determine how closely species are related to one another. Which two species are most closely related based on these nucleotide sequences?

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